Eggs as represented by chicken eggs and the like include, in addition to eggs for eating, eggs for producing chicks, eggs for manufacturing vaccines, and the like. Such eggs are called “hatching eggs” in particular. Hatching eggs are placed in an apparatus that provides a prescribed environment, such as a constant temperature, as in an incubator, and are then incubated. In an incubator, hatching eggs are loaded onto a dedicated tray, which is called a setter tray, after which the incubating process is started.
In the incubating process, the day upon which the process is started is referred to as the incubation start day, and the number of days that have elapsed since the incubation start day is referred to as the incubation day count. Chicks are born on approximately the 21st day of incubation. On the 18th or 19th day of incubation, in preparation for the hatching of the hatching eggs, a procedure is performed wherein the hatching eggs are transferred from the setter tray to a dedicated tray called a hatcher tray. At the time of this transfer procedure, a prescribed inspection, such as a viability determination, is performed. In addition, with regard to hatching eggs for the manufacture of vaccines, a prescribed inspection, such as a viability determination, is performed on the hatching eggs on the 10th day of incubation immediately prior to the injection of a virus.
Incidentally, in the hatching process, not all the hatching eggs develop normally; for example, a certain percentage of eggs are unfertilized from the start; in addition, there are developmentally stopped eggs, which are eggs wherein the development of the embryos has adversely stopped during the incubating process. The contents of such unfertilized eggs, developmentally stopped eggs, and the like have adversely rotted, and such eggs are called rotten eggs.
Usually, hatching eggs for the production of chicks are inoculated with a vaccine in the hatching egg state in order to reduce their risk of becoming infected with a contagious disease and the like after hatching; however, when hatching eggs housed in the setter tray are inoculated with a vaccine, there are cases wherein those hatching eggs whose internal pressure has risen due to rotting adversely explode because of the shock that occurs when a hypodermic needle makes contact with the shell. In addition, although such hatching eggs may not explode, the hypodermic needle may adversely become contaminated owing to the inoculation of rotten eggs with the vaccine, and thereby other healthy hatching eggs may also be adversely contaminated by that contaminated hypodermic needle. Furthermore, if a hatching egg explodes after being transferred to the hatcher tray, hatched chicks may adversely become contaminated.
To prevent such explosions and contamination, an inspection is performed that separates the hatching eggs into “viable eggs,” which are hatching eggs whose embryos are viable, and “inviable eggs,” which are, for example, unfertilized eggs or developmentally stopped eggs wherein the embryos have died. Namely, a hatching egg viability determination is performed. Conventionally, optical techniques are principally employed in a hatching egg viability determination. In one of these techniques, the viability determination is performed by radiating a hatching egg with prescribed light and then analyzing time varying components of the light that transmits through the hatching egg. In so doing, hatching eggs that have been determined to be inviable eggs are promptly eliminated, which prevents viable eggs from becoming contaminated.
The time varying components of the light that transmits through a viable egg include information related to biological activity called vital signs, such as the motility of the embryo, the heart rate of the embryo, and the like; however, the time varying components of the light that transmits through a developmentally stopped egg, wherein the embryo has died, do not contain vital signs. Accordingly, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2011-106892) proposes an apparatus that determines the viability of a hatching egg based on the presence of these vital signs.